This invention relates to a circuit for measuring electrical properties such as the resistance, capacitance and inductance. More particularly, the present invention relates to such a circuit including a bridge circuit having a component which varies with the quantity under measurement.
In known constructions of bridge circuits, the resistances of bridge branches are balanced with respect to one another as far as possible. Only minor variations are permitted to the resistance which is measurement-dependent for a direct evaluation of the diagonal voltage. In a so-called zero method, an imbalance to the diagonal voltage produced by a variation to the measurement-dependent component causes a corresponding variation at another component in the bridge circuit until the diagonal voltage is again zero. The variation in the additional component is the measurement signal. In both forms of the above-measuring bridges, the bridge branches are fed from a common voltage supply. For an adequately-accurate measurement, the known constructions of measuring bridges require a large capital outlay for components to achieve the compensation required for measuring the variation. Otherwise, the measuring bridge can be used only in a small measurement range of resistance.